c_meyer/pxt-calliope

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Peli de Halleux 2c39e249f9 New guitar project (#264 )

2016-09-26 21:55:39 -07:00

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Accelerometer Beat control

@description micro:bit guitar: using accelerometer to control tempo

~avatar avatar

Use the Accelerometer to control guitar tempo

Duration: 30 - 45 minutes
Concepts:
- Gravity
- Acceleration
- X, Y, Z coordinates
- Tempo
- Beat
- Mapping
- Graphing
- Absolute value

~

accelerometer controlled tempo
https://youtu.be/h_gPkBaVkoo TODO: add sound to video

Blocks

input.acceleration(Dimension.Y)
music.setTempo(120)
pins.map(0, 0, 1023,60, 320)
Math.abs(1)

Accelerometer, gravity and tilting!

The micro:bit contains an accelerometer sensor that is able to measure forces applied to the board. On earth, we are subject to the gravity force which pulls us to the ground!

https://youtu.be/0SULoTKmkhI

When the micro:bit is flat on a table, with the screen pointing up, the gravity force is aligned with the Z axis of the micro:bit.

If you tilt it up and down, the force will align with the Y axis -- this is how we can detect tilting!!! If the force along Y grows, the micro:bit is tilting more and more vertically!

Measuring Acceleration along different coordinates (X, Y, Z axis)

The acceleration block approximately measures milli-g, which is 1/1000 of a g or the acceleration of gravity.

Step 1: Graphing acceleration

basic.forever(() => {
    led.plotBarGraph(input.acceleration(Dimension.Y), 1023)
})

Create the code that measures the change in the Y axis acceleration as a graph on the LEDs

Dowload the code to the micro:bit

Test the movements that move the graph from 1 to 5 bars on the LEDs

Extra

Try graphing the acceleration along the X and Z axis. Can you explain the differences?

~hint

Mapping

It is common to map one standard to another - such as with temperature

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Step 2: Mapping acceleration to Beat

micro:bit sensors produce signal values between 0 to 1023. The map block converts the signal to a desired range.

basic.forever(() => {
        music.setTempo(pins.map(Math.abs(input.acceleration(Dimension.Y)),
            0, 1023,
            60, 320))
         music.playTone(Note.C, music.beat(BeatFraction.Quarter));
})

Create the code that Maps Y axis acceleration as tempo

Download the code to the micro:bit on the guitar

Test the movements that speed and slow the tempo

Step 3: Combine with light sensor tone control

Put it all together!

basic.forever(() => {
        music.setTempo(pins.map(Math.abs(input.acceleration(Dimension.Y)),
            0, 1023,
            60, 320))
        music.playTone(
            input.lightLevel() * 25,
            music.beat(BeatFraction.Quarter)
        );
})

Combine the code above with the light sensor tone control code from the previous activity